Sole for m-type travelling wave tubes



May 4, 1965 M. FAVRE SOLE FOR M-TYPE TRAVELLING WAVE TUBES Filed March 7, 1961 INVENTORZ Mum/c5 FA VRE 5y i M 7 ATTORNEYS United States Patent 3 Claims. 61. 315-395 The present invention relates to travelling wave tubes, and more particularly to the construction of the sole in socalled M-type travelling wave tubes.

In the M-type travelling wave tubes of circular form, the negative electrode, commonly called sole, is normally realized in cylindrical form, either of solid or hollow and opened construction with walls that are more or less thin. The cathode which is generally arranged within the surface of the sole is fed by means of connections carried at a relatively high negative potential with respect to the anode circuit of the tube. 4

In the known prior art devices, these connections are disposed on -the inside of the tube within the very high electric fields lot which they themselves disturb the distribution, which results in a particularly strong field concentration on the surface thereof. Consequently, if, in particular, the tube in question is a tube of very high power which'fu'nctions' under pulsed operation with a very high anode voltage, it will be readily realized that these static electric fields to which are superimposed the intense electromagnetic high frequency fields during pulsed operation of the tube, are susceptible to cause starting or striking of sparks or arcs, either of temporary or permanent nature, between the anode circuit and the cathode connections. These breakdowns have been effectively noted in practice and the proper operation of the tube has been found to be detrimentally affected thereby.

Accordingly, the present invention has for its object a tube in which the aforementioned inconveniences and shortcomings are eliminated.

It is another object of the present invention to provide a sole construction in which the danger for arcing or sparking are substantially minimized if not completely eliminated.

Still a further object of the present invention resides in the provision of an M-type travelling wave tube provided with a circular sole in which the connection, particularly the connections to the cathode are so arranged as to minimize the possibility of arcing in the tube.

Still another object of the present invention resides in the arrangement of the connections to the sole of an M- type travelling wave tube having relatively high electric fields in which the distributions of these fields are unaffected by the lead-in wires to the sole.

These and other objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawing, which shows, for purposes of illus tration only, one embodiment in accordance with the present invention which is illustrated therein in partial axial longitudinal cross sectional view.

According to the present invention, at least a portion of the sole is realized in the form of a box forming a Faraday-cage in which are accommodated the cathode conductors and the insulating supports of the cathode.

The sole may be realized by assembling any desired number of separated pieces which may be of metal having thin walls and of which one forms the closure lid of the box.

The connections of the sole and of the cathode may leave the tube axially in the form of a coaxial line in 3,182,225 Patented May 4, 1965 which the connections to the cathode pass on the inside of those leading to the sole.

Referring now to the drawing which shows, in the axial cross sectional view thereof, one embodiment of an M- type travelling wave tube of circular construction, shown therein for purposes of illustration only, reference numeral 1 designates therein the anode ring which supports thereon a delay circuit of any desired shape and construction. The enclosure of the tube is closed off by two lateral closure members 2 and 3. The annular pole pieces 4 and 5 provide the axial magnetic field necessary for proper operation of the tube.

Reference numeral 6 designates the sole of the tube which, according to the present invention, is realized in the form of a box, for example, of crimped molybdenum sheets, provided with a cover 7 which is emplaced after having effected the mounting of the connections on the inside of the box. The cover 7 may be, for example, of tantalum to act as gettering metal. Within the surface of the sole 6, there is provided, as usual, a notch or recess in which is accommodated the cathode, schematically indicated by the rectangle 8, which cathode is heated by filament 9. The insulating supports of the cathode which may be of any known construction and are understood to be comprised within the schematic rectangle 8 representing the same are contained on the inside of the box formed by the sole. The box is supported by an axial support It) in the form of a hollow column of which the inside communicates with the inside of the box. A metallic ring 11 forming aterminal intended to be connected to the voltage source of the sole 6 is secured to the free end of support 10. The vacuum-tight enclosure of the tube is completed by a Kovar ring 12, brazed to the cover member 2 and soldered, on the other end, to a glass ring 13, a Kovar ring 14 connecting the glass ring 13 to the metallic ring 11, and a Kovar ring 15 connecting the metallic ring 11 to the base portion 16 of insulating material. Two cathode connections 17 pass through the insulating base portion 16, thereupon proceed on the inside of the support 10, and thereafter enter the inside of the box 6, 7 where they are connected to the terminals of the filament 9, one of the connections being also connected to the cathode 8.

The connections 17 are thus completely shielded, initially by the sole 6, 7, and thereupon by the connection 10 of the sole.

Experiments have indicated that with this arrangement the undesirable phenomena mentioned hereinabove completely cease to exist. It follows therefrom that with the tubes utilizing the present invention, it is no longer requisite to observe the electric distances dimensioned as large as within the known prior art tubes, which in turn offers the possibilities of reduction, with the same voltage, of the dimensions of the tubes, and by the correlary, of the weight of the magnets necessary for the operation thereof. Additionally, the shielding realized in accordance with the present invention permits protection of the insulating pieces utilized on the inside of the tube against soiling by the projection of particles derived or coming from the gettering material. Additionally, it also avoids certain undesirable high frequency couplings.

While I have shown and described one embodiment in accordance with the present invention, it is understood that the same is not limited thereto but is susceptible of many changes and modifications as appears obvious to a person skilled in the art. In particular, only a portion of the sole may be realized in the form of a box, the other portion being of any desired construction. The walls of the portion of the sole constructed as a box may be either thin or heavy, and any particular manner of subdividing the same into separate pieces in no way a, G affects the spirit or scope of the present invention which encompasses all realizations in which the structure of the sole forms effectively a Faraday-cage for the cathode connections. I

Thus, it is obvious that the present invention is not limited to the details shown and described herein, but is susceptible of many changes and modifications within the spirit and scope thereof, and I, therefore, do not wish to be limited to the details shown and described herein but intend to cover all such changes and modifications as are encompassed by the scope of the appended claims.

I claim:

1. An M-type travelling wave tube of essentially circular structure having its axis essentially coinciding with the lines of force of the operating magnetic field, comprising essentially circular anode electrode means, sole electrode means of circular shape and essentially coaxial with said anode electrode means, emissive cathode means including insulating support means for supporting said cathode means on said sole electrode means, and energizing leads leading to said cathode means, at least a portion of said sole electrode means being a hollow box elfectively forming a Faraday cage for accommodating therein said cathode support means and said leads, said box being essentially composed of a body portion and of an essentially plane cover closing the space within said body portion.

2. An M-type travelling wave tube of essentially circular structure having its axis essentially coinciding with the lines of force of the operating magnetic field, comprising essentially circular anode electrode means, sole electrode means of circular shape and essentially coaxial with said anode electrode means, emissive cathode means including insulating support means for supporting said cathode means on said sole electrode means, and energizing leads to said cathode means, at least a portion of said sole electrode means being a hollow box effectively forming a Faraday cage for accommodating therein said cathode support means and said leads, said box being essentially composed of a body portion and of an essentially plane cover closing the space within said body portion, said cover being made of gettering material.

3. An M-type travelling wave tube of essentially circular structure having its axis essentially coinciding with the lines of force of the operating magnetic field, comprising essentially circular anode electrode means, sole electrode means of circular shape and essentially coaxial with said anode electrode means, emissive cathode means including insulating support means for supporting said cathode means on said sole electrode means, and energizing leads leading to said cathode means, at least a portion of said sole electrode means being a hollow box eifectively forming a Faraday cage for accommodating therein said cathode support means and said leads, said box being essentially composed of a body portion and of an essentially plane cover closing the space within said body portion, said cover being made of gettering material essentially consisting of tantalum.

References Cited by the Examiner UNITED STATES PATENTS 2,538,053 1/51 Smith 313-355 X 2,760,111 8/56 Kumpfer 3l5-39.3 2,907,913 10/59 Dench 315-393 X GEORGE N. WESTBY, Primary Examiner. ARTHUR GAUSS, Examiner. 

1. AN M-TYPE TRAVELLING WAVE TUBE OF ESSENTIALLY CIRCULAR STRUCTURE HAVING ITS AXIS ESSENTIALLY COINCIDING WITH THE LINES OF FORCE OF THE OPERATING MAGNETIC FIELD, COMPRISING ESSENTIALLY CIRCULAR ANODE ELECTRODE MEANS, SOLE ELECTRODE MEANS OF CIRCULAR SHAPE AND ESSENTIALLY COAXIAL WITH SAID ANODE ELECTRODE MEANS, EMISSIVE CATHODE MEANS INCLUDING INSULATING SUPPORT MEANS FOR SUPPORTING SAID CATHODE MEANS ON SAID HOLE ELECTRODE MEANS, AND ENERGIZING LEADS LEADING TO SAID CATHODE MEANS, AT LEAST A PORTION OF SAID SOLE ELECTRODE MEANS BEING A HOLLOW BOX EFFECTIVELY FORMING A FARADAY CAGE FOR ACCOMMODATING THEREIN SAID CATHODE SUPPORT MEANS AND SAID LEADS, SAID BOX BEING ESSENTIALLY COMPOSED OF A BODY PORTION AND OF AN ESSENTIALLY PLANE COVER CLOSING THE SPACE WITHIN SAID BODY PORTION. 